全文获取类型
收费全文 | 3089篇 |
免费 | 68篇 |
国内免费 | 19篇 |
专业分类
电工技术 | 190篇 |
综合类 | 5篇 |
化学工业 | 1026篇 |
金属工艺 | 96篇 |
机械仪表 | 105篇 |
建筑科学 | 93篇 |
能源动力 | 141篇 |
轻工业 | 192篇 |
水利工程 | 6篇 |
石油天然气 | 3篇 |
无线电 | 152篇 |
一般工业技术 | 704篇 |
冶金工业 | 105篇 |
原子能技术 | 121篇 |
自动化技术 | 237篇 |
出版年
2023年 | 17篇 |
2022年 | 47篇 |
2021年 | 53篇 |
2020年 | 23篇 |
2019年 | 32篇 |
2018年 | 52篇 |
2017年 | 45篇 |
2016年 | 61篇 |
2015年 | 49篇 |
2014年 | 70篇 |
2013年 | 166篇 |
2012年 | 105篇 |
2011年 | 201篇 |
2010年 | 140篇 |
2009年 | 146篇 |
2008年 | 172篇 |
2007年 | 116篇 |
2006年 | 135篇 |
2005年 | 117篇 |
2004年 | 84篇 |
2003年 | 116篇 |
2002年 | 82篇 |
2001年 | 55篇 |
2000年 | 68篇 |
1999年 | 56篇 |
1998年 | 87篇 |
1997年 | 83篇 |
1996年 | 67篇 |
1995年 | 43篇 |
1994年 | 35篇 |
1993年 | 45篇 |
1992年 | 30篇 |
1991年 | 29篇 |
1990年 | 32篇 |
1989年 | 46篇 |
1988年 | 31篇 |
1987年 | 34篇 |
1986年 | 53篇 |
1985年 | 45篇 |
1984年 | 56篇 |
1983年 | 49篇 |
1982年 | 32篇 |
1981年 | 24篇 |
1980年 | 19篇 |
1979年 | 27篇 |
1978年 | 19篇 |
1977年 | 18篇 |
1976年 | 11篇 |
1974年 | 14篇 |
1973年 | 10篇 |
排序方式: 共有3176条查询结果,搜索用时 0 毫秒
71.
The mechanism of enhanced PVC impact strength of poly(vinyl chloride) modified by an acrylic graft copolymer was studied by the three-point bending test on a U-notched bar. In the mechanism, the void formation from the modifier released the constrained strain. The release suppresses the stress below the fibril strength in the material; consequently, stable deformation can develop over a large area and, thus, the impact strength of PVC modified by the acrylic graft copolymer is improved. © 1996 John Wiley & Sons, Inc. 相似文献
72.
The swelling and adsorption behavior of poly(N-isopropylacrylamide)–SiO2 hybrid gels, derived from copolymerization of N-isopropylacrylamide and 3-methacryloxypropyltrimethoxysilane (MPTMOS) and following hydrolysis and condensation, were investigated. The hybrid gels exhibited temperature dependence of both the swelling ratio and adsorption of solutes, and their temperature dependence of both the swelling ratio and adsorption of solutes, and their temperature dependence was related to the MPTMOS content in the hybrid gels. In addition, the modification of thermosensitive properties of the hybrid gels could be achieved by treatment with other silane compounds. © 1996 John Wiley & Sons, Inc. 相似文献
73.
In this article, two kinds of perfluoropolyether (PFPE) with different terminal groups were investigated using thermogravimetric analysis (TGA), infrared (IR) spectroscopy, gel permeation chromatography (GPC), and gas chromatography/gas mass spectrum (GC/MS) analysis. PFPEs with a hydroxyl or carboxylic acid terminal group were more heat stable than was PFPE with carboxylic methyl ester. Perfluoropropylene oxide-type PFPE with a perfluoroethyl terminal group at one end tends to lose weight more rapidly than does copolymer-type PFPE with dihydroxyl or dicarboxyl methyl ester terminal groups at both ends. The residual weight fraction of PFPE with a perfluoroethyl terminal group was dependent on the average molecular weight. The number-average molecular weight of PFPE can be calculated from the peak intensity ratio between the polar group and C F stretching by measuring the IR spectrum of PFPE. The number-average molecular weight of PFPE increased because of the evaporation loss of its low molecular weight fraction and the crosslinking reaction of PFPE with increase in temperature. GC/MS analysis showed that the main product of the pyrolysis of PFPE was hexafluoropylene. We speculated on the PFPE degradation mechanism and the optimum PFPE chemical structure in terms of heat stability. © 1996 John Wiley & Sons, Inc. 相似文献
74.
Akira Ichikawa 《国际强度与非线性控制杂志
》1996,6(5):431-452
》1996,6(5):431-452
The H∞-control problem with a non-zero initial condition for infinite dimensional systems is considered The initial conditions are assumed to be in some subspace. First the H∞ problem with full information is considered and necessary and sufficient conditions for the norm of an input-output operator to be less than a given number are obtained, The characterization of all admissible controllers is also given. This result is then used to solve the general H∞ control problem and the filtering problem with initial uncertainty. The filtering problem on finite horizon involves the estimate of the state at final time. The set of all suboptimal filters is given both on finite and infinite horizons. 相似文献
75.
The objective of this study is to evaluate simultaneously the time dependence of the thermal diffusivity of carbon-carbon composites (C/C composites) and their porosity during heat treatment using the electromagnetic ultrasonic technique. This paper describes two kinds of experiments conducted to confirm the principle for simultaneous measurement of both the ultrasonic velocity (used to evaluate the porosity) and the thermal diffusivity at room temperature. For each material, the samples used in both experiments were identical. The ultrasonic velocity of type 304 stainless steel and its thermal diffusivity were 5.85 km/s and 3.8 mm2/s with precisions of ±1.6 and ±8 percent, respectively. The ultrasonic velocity of a two-dimensional woven C/C composite and its thermal diffusivity were 2.86 km/s and 4.8 mm2/s with precisions of ±5.0 and ±8 percent, respectively. The results appear to indicate that the electromagnetic ultrasonic technique can measure the ultrasonic velocity and the thermal diffusivity simultaneously and that it is also applicable to C/C composites. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res, 25(5): 308–322, 1996 相似文献
76.
Tae Oike Yoshihito Sekiguchi Yuya Yoshimoto Takahiro Oike Ken Ando Wenchao Gu Yasushi Sasaki Takashi Tokino Akira Iwase Tatsuya Ohno 《International journal of molecular sciences》2022,23(1)
Radiotherapy is a definitive treatment for early-stage cervical cancer; however, a subset of this disease recurs locally, necessitating establishment of predictive biomarkers and treatment strategies. To address this issue, we performed gene panel-based sequencing of 18 stage IB cervical cancers treated with definitive radiotherapy, including two cases of local recurrence, followed by in vitro and in silico analyses. Simultaneous mutations in KRAS and SMAD4 (KRASmt/SMAD4mt) were detected only in a local recurrence case, indicating potential association of this mutation signature with radioresistance. In isogenic cell-based experiments, a combination of activating KRAS mutation and SMAD4 deficiency led to X-ray resistance, whereas either of these factors alone did not. Analysis of genomic data from 55,308 cancers showed a significant trend toward co-occurrence of mutations in KRAS and SMAD4. Gene Set Enrichment Analysis of the Cancer Cell Line Encyclopedia dataset suggested upregulation of the pathways involved in epithelial mesenchymal transition and inflammatory responses in KRASmt/SMAD4mt cancer cells. Notably, irradiation with therapeutic carbon ions led to robust killing of X-ray-resistant KRASmt/SMAD4mt cancer cells. These data indicate that the KRASmt/SMAD4mt signature is a potential predictor of radioresistance, and that carbon ion radiotherapy is a potential option to treat early-stage cervical cancers with the KRASmt/SMAD4mt signature. 相似文献
77.
Sae Saigo Tabito Kino Kotaro Uchida Takuya Sugawara Lin Chen Michiko Sugiyama Kengo Azushima Hiromichi Wakui Kouichi Tamura Tomoaki Ishigami 《International journal of molecular sciences》2022,23(1)
The prorenin/renin receptor ((P)RR) is a multifunctional protein that is widely distributed in various organs. Despite intensive research for more than 20 years, this receptor has not been fully characterized. In this study, we generated mice overexpressing the tubular epithelial (P)RR gene ((P)RR-TG mice) to test the previously reported functional role of (P)RR by Ramkumar et al. in 2015 using tubular specific (P)RR KO mice. (P)RR-TG mice were maintained and analyzed in individual metabolic cages and were administered angiotensin II blocker (ARB), direct renin inhibitor (DRI), and bafilomycin, that is, vacuolar ATPase (V-ATPase) antagonist. (P)RR-TG mice were hypertensive and had alkalized urine with lower osmolality and Na+ excretion. ARB and DRI, but not bafilomycin, concurrently decreased blood pressure. Bafilomycin acidized urine of (P)RR-TG mice, or equivalently this phenomenon restored the effect of overexpressed transgene, suggesting that (P)RR functioned as a V-ATPase in renal tubules. Afterall, (P)RR-TG mice were mated with alternative renin transgenic mice (ARen2-TG), which we identified as intracellular renin previously, to generate double transgenic mice (DT-TG). Lethal renal tubular damage was observed in DT-TG mice, suggesting that intracellular renin may be a ligand for (P)RR in tubules. In summary, (P)RR did not substantially affect the tissue renin-angiotensin system (RAS) in our model of tubular specific (P)RR gene over-expression, but alternative intracellular renin may be involved in (P)RR signaling in addition to conventional V-ATPase function. Further investigations are warranted. 相似文献
78.
Sakai K Mori M Fujii A Iwami Y Chukeatirote E Shirai Y 《Journal of Bioscience and Bioengineering》2004,98(1):48-56
Reproducible amounts of lactic acid accumulate in minced kitchen refuse under open conditions with intermittent pH neutralization [Sakai et al., Food Sci. Technol. Res., 6, 140 (2000)]. Here, we showed that such pH-controlled open fermentation of kitchen refuse reproducibly resulted a selective proliferation of a major lactic acid bacterial (LAB) species. In one experiment, the predominant microorganisms isolated during the early phase (6 h) were Gammaproteobacteria. In contrast, those that predominated during the late phase (48 h) were always Lactobacillus plantarum in three independent experiments. To further quantify the microbial community within open lactic acid fermentation, we performed fluorescent in situ hybridization (FISH) analysis targeting 16S (23S) rRNA. We designed two new group-specific DNA probes: LAC722(L) was active for most LAB including the genera Lactobacillus, Pediococcus, Leuconostoc and Weisella, whereas Lplan477 was specific for L. plantarum and its related species. We then optimized sample preparation using lysozyme and hybridization conditions including temperature, as well as the formamide concentration and the salt concentration in the washing buffer. We succeeded in quantification of microorganisms in semi-solid, complex biological materials such as minced kitchen refuse by taking color microphotographs in modified RGB balance on pre-coated slides. FISH analysis of the fermentation of kitchen refuse indicated that control of the pH swing leads to domination by the LAB population in minced kitchen refuse under open conditions. We also confirmed that L. plantarum, which generates lactic acid in high quantities but with low optical activity, became the dominant microorganism in kitchen refuse during the late phase of open fermentation. 相似文献
79.
Toshiharu Nagatsu Akira Nakashima Hirohisa Watanabe Shosuke Ito Kazumasa Wakamatsu 《International journal of molecular sciences》2022,23(8)
Parkinson’s disease (PD) is an aging-related disease and the second most common neurodegenerative disease after Alzheimer’s disease. The main symptoms of PD are movement disorders accompanied with deficiency of neurotransmitter dopamine (DA) in the striatum due to cell death of the nigrostriatal DA neurons. Two main histopathological hallmarks exist in PD: cytosolic inclusion bodies termed Lewy bodies that mainly consist of α-synuclein protein, the oligomers of which produced by misfolding are regarded to be neurotoxic, causing DA cell death; and black pigments termed neuromelanin (NM) that are contained in DA neurons and markedly decrease in PD. The synthesis of human NM is regarded to be similar to that of melanin in melanocytes; melanin synthesis in skin is via DOPAquinone (DQ) by tyrosinase, whereas NM synthesis in DA neurons is via DAquinone (DAQ) by tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC). DA in cytoplasm is highly reactive and is assumed to be oxidized spontaneously or by an unidentified tyrosinase to DAQ and then, synthesized to NM. Intracellular NM accumulation above a specific threshold has been reported to be associated with DA neuron death and PD phenotypes. This review reports recent progress in the biosynthesis and pathophysiology of NM in PD. 相似文献
80.
Tetsuya Nanba Asima Sultana Shouichi Masukawa Masaaki Haneda Junko Uchisawa Akira Obuchi Hideaki Hamada 《Topics in Catalysis》2009,52(13-20):1766-1770
Selective catalytic reduction of NO x by NH3 over Cu–FER and Cu–ZSM-5 in the presence of n-decane and SO2 was investigated. NO x conversion over Cu–ZSM-5 decreased in the presence of n-decane, owing to inhibition of the active sites by coke formation. In contrast, coke formation was negligible over Cu–FER, which maintained its NO x conversion activity even in the presence of decane. Coke formation was negligible over H–ZSM-5 and H–FER supports, which suggests that Cu species were involved in coke formation. Temperature-programmed reduction by H2 and electron spin resonance spectroscopy indicated that [Cu–O–Cu]2+ was probably the Cu species involved in coke formation over Cu–ZSM-5. 相似文献